Electrical apparatus



' Oct. 14, 1924. 1,511,717

L. F. BLUME ET AL ELECTRICAL APPARATUS 1 Filed Oct. 18. 1920 4 Sheets-Sheet 1 Inventors: Louis TTBlume, John S.Lenno The i r" Atlto Pney.

Oct. 14. 1924- 1,511,717

L. F. BLUME ET AL ELECTRI CAL APPARATUS Filed Oct. 18. 1920 4 Sheets-She s: 2

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Inventors: Louis FTBlume, John $.Lennox,

TheirAttorn e y Oct. 14, 1924.

L. F. BLUME ET AL.

ELECTRICAL APPARATUS Filed Oct. 18. 1920 Fig.6

4 Sheets-Sheet 5 Inventors: Loui s FTBI ume, John $.Lennox .M The irAttorney.

v L. F, BLUME ET AL ELECTRICAL APPARATUS Oct. 14. 1924- -'1-,511,717

Filed Oct. 18 1920 4 Sheets-Sheet Inventor-s.-

Louis FTBlurne, JohnSLennoX, WM

TheirAtto Pney,

Patented Oct. 14, 1924.

UNITED STATES 1,511,717 PATENT OFFICE.

LOUIS l. BLUME, OF ItITTSFIELD, MASSACHUSETTS, AND JOHN S. LENNOX, OF NOE- WICH, CONNECTICUT, ASSIGNORS T GENERAL ELECTRIC COMPANY, A CORPORA- TION OF NEW YORK.

ELECTRICAL APPARATUS.

Application filed October 18, 1920. Serial No. 417,704.

To all whom it may concern:

a citizen of the United States, and JOHN S. LENNOX, a subject of the King of Great Britain, residing, respectively, at Pittsfield, county of Berkshire, State of Massachusetts, and at Norwich,county of New;London, State of Connecticut, have invented certain new and useful Improvements in Electrical Apparatus, ofwhich the followin is a specification.

%ur invention relates to electrical apparatus having windings with one end grounded and having distributed capacitance, and has for its general object an improved arrangement 0 parts for securing a desired initial voltage distribution. More particularly our invention relates to an improved protecting and voltage distributing means used in conjunction with the, capacitance of the windings of stationary induction apparatus having one end grounded,

11 an electrical'winding, when an abrupt voltage or impulse is applied to its terminals, the initial voltage distribution is determined entirely by the capacitance present in the winding and not by the inductances. The capacitance of the winding consists of the entire series and parallel arrangement of capacity elements existing throughout the winding from one terminal to the other, including capacity from the winding to ground and capacity from one part of the winding to another. The charging of the various capacity elements tothe respective potentials corresponding to the initial voltage distribution is eflt'ected by current which does not flow along the winding, or through its inductance, but only through other series elements of capacitance.

The passage of such currents, in electrical apparatus as ordinarily designed causes a concentration of voltage at the line end of the winding. This voltage distribution is of very short duration, however, because as soon as the growing current flowing inductively through the winding can grow to an appreciable value the inductive effect of these growing currents causes a rapid modification of the initial voltage distribution. The reaction between the capacitance and inductive efiects gives rise to oz cillations within the winding, thereby causing an objectionable concentration of potential on the interior of the winding. Moreover, if the impulses are applied periodically at a frequency corresponding with the natural oscillat-ing frequency of the transformer, the potential concentrations may grow very rapidly to values in excess of the ability of the insulation to withstand.

It has been discovered that if the capaci tance associated with the inductance of any winding be disposed in such a manner that the potential gradient which would be produced by the capacitance alone is the same as that which would be produced by the inductance alone, then in the first place there will be no concentration of potential on the end turns of the winding due to the application of an abrupt impulse, and in the second place the internal oscillations produced by periodically applied impulses will be negligible; the application of which principle is set forth in the patent a plication filed in the name of J. M. Weed, Serial No. 354,896, on January 29, 1920. It has further been discovered that the desired distribution practical requirements. In carrying out our lnvention we employ an auxiliary condenser system comprising generally one element so shaped an spaced from the windings that when secured in position at one side of the winding it secures substantially the desired voltage distribution.

For a more complete understanding of the nature and objects of our invention, reference should be had to the following detailed description when taken in connection with the accompanying drawings, in which Figs. 1 and 2 are explanatory diagrams, Fig. 3 shows in symbolic fashion an embodiment of our invention, Fig. 4 is a similar figure showing a modified arrangement, Fig. 5 is a view 'partly in section and partly in side elevation of a transformer constructed to embody our invention, and Figs. 6 and 7 e I a I A! are similar views of another embodlment of our invention as applied to transformers.

Referring now to the drawlngs, and to -Fig. 1 in particular, we have indicated a winding at W, the elements of which are represented as'having inherent series capac itance between the turns by the condensers shown at; G, and inherent shunt or ground capacitance by the condensers shown at G.

7 K etc. The condenser elements K K K- etc., are connected in series and are graded ofl at a uniform rate from the line end is the arrangement invariably employed in the practice of our invention.

In Fig. 4 is shown a winding provided with a single metallic condenser element for securing the capacity distribution symbolically depicted in Fig. 3.

Here the winding 10 is shown on core 11, having an end grounded at 12, the other leading to the line at 13 as before. A generally conical metallic plate 15 is disposed about but does not entirely encircle the winding 10, the smaller end of the cone fitting against the line or to turn of the winding 10 and being conductively related thereto. The lower end 16 of the cone is belled out in order to approximate the rapid diminuctiion of the capacity required at ground en To shield completely a grounded winding in accordance with our invention, we contemplate the use of a conical end plate, as indicated at 17, to be used in conjunction with the element 15; such end plate being detoward the ground end which is indicated by'- scribed in the afplication for U. 5. Letters the diiference in the size of these elements as .must'be suflicient to supply charging current to condensers K K etc., and to the shunt condenser G Thus as we progress toward ground end less charging current is needed or the series of condensers K,, K etc.

In Fig. 2 there is shown an equivalent'arrangement of compensatin capacitance, comprising the condensers H H etc., which are connected in parallel ,to each other and all supplied with charging current from the line a through conductor; 03. Obviously,

. in this arrangement condenser H should be only suliicient to sup 1y condenser G with- .charglng current, an likewise condenser H but sufficient to supply condenser G etc.

In Fig. 3 we have symbolically depicted an application of this arrangement of an external condenser or condensers to. a disccoil winding 10- on a core 11; which windin has one terminal grounded at 12, the other ead- I ing to the line at 13. The capacity elements h k k etc. of the external condenser are shown as connected in parallel to the line lead13through conductor 14, while the other sides of the elements are conductively' related to progressive points in the winding 10. This symbolic depiction of an arrangement of capacity elements, to efi'ecta voltage distribution electrostatically in winding 10 which would be the same as that due to the inductance were'the capacity non-existent,

Patent filed by M. Weed, Ser. No. 396,585. This end plate, however, may be omitted and is not shown in the further views of the drawings in the interest of clearness.

' In 1 1g. 5 we have illustrated our inven ti on app-lied to a transformer in a more practicalform of condenser device than the shown in Fig. 4.

In Fig. 5 a three-legged core 20 is repre sented as having windings surrounding its central leg. These winding are represented as comprising a low Volta e cylindrical winding 21 supported in the esired spaced relation from the central leg by means of the insulating cylinder shown at 22. The high voltage winding comprises disccoils 23 supr ported in proper spaced relation by means of the spacing devices 24 which abut at the rear against insulating cylinders 25 placed between the high and lowvoltage windings.

- The high voltage winding 23, as shown, has. its grounded end at the top as indicated I otential elevation above ground are at the bottom. I Consequently the insulating barriers shown at 26 are inserted between the lowermost coil and the coil supporting abutments 2'? on the lower end of the core. To efi'ect substantially. thedesired voltage distribution in this transformer according to our invention, two substantially triansymbolically. at 6 so that the coils of greatest loo , gular metallic'plates 30 and 30' are secured, Y

one at each side, on the coil stack adjacent the high voltag winding, and are conductlvely' related to the lowermost coil.

As previously indicated, the coils at greatest potential elevation have associated therewith the capacity elements of greatest capacitance. Accordingly, the lowermost coil has the lower end of plates 30 end 30' nearest to it and also has adjacent to it I the greatest peripheral extent of the plates 30 and 30'; that is, the bases of the triangular configuration of these plates follow the circumference of the 'coil. The coil next to the bottom, by the arrangement previously symbolically depicted, has less capacitance associated with it :so that the plates 30 and 30 are spaced further from it than from the bottom one; also there is less of the peripheral extent of these plates associated with the second coil. This gradual decrease in the capacity elements to be associated with the coils 23 as we approach ground potential occasions the general triangular configuration of the plates 30 and 30. While these plates will in general have this particular configuration it is merely incident to the design in properly proportioning the capacitance among the turns and we do not intend to be limited thereby to any specific configuration of plates, but

propose to alter the same as the exigencies of the case may indicate.

Insulatin cylinders 31 are shown as surrounding t eupper end of high voltage coils 23, and are employed partly for protecting and insulating urposes and also for aiding in securing t e proper spacing of the la-tes 30 and 30' from the coil stack.

In igs. 6 and 7 we have shown another arran ement for applying our invention to trans ormers. Here again, a three-legged core 40 has windings supported about its central leg. The low voltage winding 41 is of the cylindrical type and is supported in proper spaced relation to the core by insulating cylinder 42, which winding in turn. is separated from the high voltage winding comprising coils 43, by the insulating cylinder 44. The coils 43, are shown, as before, spaced apart by spacing devices 45 and supported by coil supporting abutment 47.

The upper end of the coil stack in this instance is connected to the line, as indica-ted by the lower end of the bushing structure 50 which has a conductor 51 leading therefrom to the winding. The ground con-. nection is at the lower end as indicated symbolically at f in Fig. 7.

The voltage distributing and shielding device here employed is not wholly a solid plate but is in part what may be termed a skeleton condenser element and has theobvious advantage that it in no wise impedes the free circulation of the cooling and ventilating medium, such as oil 'in which the transformer is submerged; one element being disposed on each side of the coil stack.

This so-called skeleton condenser element is composed of suitably arranged conductors. The conductors here employed are ,strap conductors, shown at 55 of U-shaped configuration having each leg disposed adjacent the periphery of a coil 43. The ends of the legs of each U at 55 are conductively anchored in a trunk-conductor 56 which extends from the lead 51 down along one side of the coil stack to the solid or plate portion of the condenser element shown at 57, with which it is conductively connected. A portion of the Us em loyed may be and preferably are formed oi round conductors as shown at 58 and comprise an intermediate portion of the device. Round; conductors can with advantage be employed where it is not desired to have the capacity elements as closely associated with the coils 43 as at the top.

The portion of the condenser element shown at 57 is of triangular configuration and is held in proper spaced relation to the windings by any suitable construction. that shown comprising vertically disposed braces 60 and 60 which are secured at their tops to the coil clamping ring 61 on opposite sides and at their bottoms to the core supporting base 62. These braces are preferably made of insulating material, for instance paraflin treated wood, and have a' shape on their inner sides, such that when the plates 57 are drawn u thereagainst as by bolts 59, the plates are held in proper spaced relation to the coils 43. Between coils 43 and each plate 57 are one or more insulating cylinders such as are shown at 63; the space between a cylinder 63 and a plate 57 under a. brace 60 being preferably made solid by the insertion o a suitably shaped insulating element, such as we have shown at 64 in Fig. 7.

The con-denser elements which were just described are substantially similar on each side of the transformer but have independent electrical connections with the line lead 51; the arrangement shown providing the proper grading of capacity elements associated with the coils 43 as we pass from line potential to the ground end of the coil stack.

The-use of tapered condenser elements in conjunction with a grounded winding, such as we have described, imposes a voltag distribution electrostatically throughout the winding to beprotected which substantially coincides with that due to the inductance of the winding when considering the capacitance as non-existent; hence there is no tendency during the interval when steep wave fronts and like transients traverse the winding for capacity charging currentto surge from one portion of the winding to another and thus set up resonant oscillations.

Having now described. several embodiments of our invention which are at present the best means known to us for carrying the same into effect, we would have it understood that these are merely illustrative and that we do not mean to be limited thereby to the precise details shown, her restricted in the choice of recognized equivalents except as defined in our claims hereunto annexed. A

What we claim as new and desire to sei I cure by Letters Patent of the United States,

ductive'ly connected to the line end of the winding and its longitudinal extent progressively spaced from the winding as the ground end is approached. I

3. In a stationary induction apparatus, the combination with a core, of a high voltage winding thereon "having one end connected to ground, and an auxiliary condenser system comprising a substantially triangular conducting plate disposed adjacent said winding, conductively connected to the line end thereof and having its apex disposed adjacent the ground end and progressively spaced therefrom as the ground end is approached.

r In witness whereof, we have hereunto set our hands and seals respectively the 29th day of Sept, 1920; and the 11th day of October, 1920.

LOUIS F. BLUME. JOHN'S. LENNOX. 

